Multi-part .rar archive. You must have all parts (e.g., part1, part2, etc.) in the same folder to successfully extract the full ISO image.
While the initial CODEX release represents the "Day 1" version of the game, user and critic reports highlight that this version had several issues that were later addressed in official updates: BIOMUTANT-CODEX.part1.rar
If you are starting the game, keep these community-recommended tips in mind: Multi-part
